1. Field of the Invention
The present invention relates to a method of manufacturing a flying magnetic head used in a magnetic disc drives and, in particular, to a method of manufacturing a flying magnetic head using a thin-film-laminated core as the head core (the head chip).
2. Description of the Related Art
FIGS. 8 and 9 show a so-called-composite-type flying magnetic head, which is generally used in a magnetic disc drives. This flying magnetic head is equipped with a slider 2 and a head core (a head chip) 1 and connected to the arm of the actuator of the drives body through a plate-spring suspension 3. The head core 1 consists of a ferrite core chip or an MIG-type core chip having a gap portion in which is formed a magnetic thin film of an Fe-Si-Al alloy (Sendust) or an amorphous magnetic material. This head core 1 is fitted into a groove 5 formed in an air-bearing-surface (hereinafter referred to simply as "ABS") portion 4 of the slider 2 and is secured therein by glass molding.
Generally, the slider 2 is formed of a non-magnetic ceramic material. Accordingly, the glass molding portion by means of which the head core 1 is joined to the slider 2, i.e., the molding glass M (FIG. 10), is softer than the head core 1 and the slider 2. As a result, this glass molding portion is liable to be recessed with respect to the other portions even in the stage of the final finish of the ABS portion 4. As is known in the art, it is very difficult to make the depth of this recess less than 100.ANG..
Such a recess is apt to allow deposit from the disc medium to gather therein due to CSS (contact start stop), with the result that the friction between the head and the disc increases, which leads to deterioration in durability. Since frictional force changes in proportion to the area involved, reducing the area of that portion of the molding glass M exposed on the ABS portion 4 would be very effective in attaining an improvement in terms of CSS characteristic.
However, in a core chip of the ferrite type or the MIG type, the width W of that portion of the head core which is exposed on the ABS portion (FIG. 9) corresponds to the track width. Accordingly, it is necessary to make exclusively the core tip portion in a thickness, for example, of 10 .mu.m by machining, whereas the thickness T of the remaining head core portion has to be not less than 100 .mu.m to secure the requisite level of handling strength. Thus, as shown in FIG. 10, the width of the exposed portion of the molding glass M, which corresponds to the difference w between the thickness W of the head-core tip portion and the entire thickness T of the head core portion, has to be as large as 90 .mu.m or more, which constitutes a very serious problem.
Further, in a conventional composite-type flying magnetic head, in which the entire head core or the principal portion thereof consists of ferrite, the entire head core functions as a magnetic core. If, with such a flying magnetic head, a higher frequency flying to be dealt with, a reduction in inductance must be effected, so that -there is no choice but to form the head core in the smallest possible thickness T of approx. 100 .mu.m to retain the requisite level of handling strength, thus attaining a reduction in inductance per number of turns. Accordingly, except for that portion of the head core which corresponds to the track width, which is only one tenth of the above thickness, the head core has to be filled with molding glass or the like. Thus, it is difficult to realize a structure in which the exposed portions on the ABS portion are restricted to the slider and core materials, which exhibit a satisfactory level of CSS characteristic.
With a view to solving the above problems, the present inventors directed their attention to a thin-film-laminated composite-type floating magnetic head, which uses a thin-film-laminated core as the head core (the head chip). Such a head core, which has recently come to be used in VCR and which helps to realize high-density recording and to attain a reduction in track width, is prepared by depositing on a substrate thin films of an Fe-Si-Al alloy (Sendust), an amorphous magnetic material, iron nitride, etc. Examples of a thin-film-laminated composite-type flying magnetic head are described in Japanese Patent Application No. 2-76365 and 2-204202, which were filed by the present applicant. As shown in FIGS. 11 and 12 of the present application, each of the flying magnetic heads of the above-mentioned patent applications is prepared by fitting a head core 1 into a given groove 5 in a ceramic slider 2, which is formed, for example, by cutting and grinding a unitary ceramic piece. The head core 1 thus fitted into the groove 5 is secured therein by glass molding.
With such a thin-film-laminated composite-type magnetic head, the track width is determined by the thickness of the magnetic alloy film 14. As shown in FIG. 11, this magnetic alloy film 14 is reinforced on either side by means of ceramic portions 11 and 16, whereby the thickness of the molding glass portions Ma, Mb and Mc, by means of which the head core 1 is bonded to the slider 2, can be substantially reduced. The thickness of these molding glass portions is reduced to 20 .mu.m or less, or even to 10 .mu.m or less. This helps to substantially reduce the exposed area on the ABS portion of the molding glass and to attain an improvement in CSS characteristic to a remarkable degree. Thus, it will be appreciated that according to the above-mentioned patent applications, a generally reliable composite head can be realized.
However, even in such a thin-film-laminated composite-type flying magnetic head, there is a demand for a further reduction in the exposed area of the molding glass on the ABS portion, i.e., a further improvement in terms of CSS characteristic. That is, the molding-glass portions Ma, Mb and Mc, by means of which the head core 1 is bonded to the slider 2, are softer than the head core 1 and the slider 2, and, even in the stage of the final finish of the ABS portion 4, these glass portions are more liable to be recessed as compared to the other portions. It is very difficult to make the depth of these recesses less than 100.ANG.. As stated above, deposit from the disc medium is apt to gather in these recesses due to CSS (contact start stop), with the result that the friction between the head and the disc medium increases, which leads to deterioration in durability.
Further, as stated above, when preparing a conventional thin-film-laminated composite-type flying magnetic head, a head core 1 is fitted into a given groove 5 in a ceramic slider 2 formed by cutting and grinding a unitary ceramic piece, and is secured in the groove 5 by glass molding. The problem with this preparation method is that the operations of forming the groove 5 by machining, fitting the head core 1 into the groove 5, performing glass molding subsequent to the fitting, etc. are very complicated and demand skill, resulting in a rather poor operational effeciency.
To solve the above problems, a method of manufacturing a thin-film-laminated composite-type flying magnetic head has been proposed in a Japanese Patent Application (Japanese Patent Laid-Open No.2-240818) filed by Kansai Nichiden Kabushiki-Kaisha. According to the method proposed, the area of those material portions other than the slider material which are exposed on the ABS portion, can be substantially reduced.
In accordance with the method mentioned above, core blocks, each formed by depositing thin magnetic films of an Fe-Si-Al alloy on a non-magnetic substrate, are bonded with each other by glass bonding to form a magnetic head block, and this magnetic head block is bonded to a slider block by resin or glass bonding to form a core/slider assembly. Then, grooving is performed on this core/slider assembly, and then, cutting on the magnetic head block, thus preparing a flying magnetic head as shown in FIG. 13.
With this flying magnetic head, constructed as described above, the portions exposed on the ABS are L restricted to the following: a metal magnetic film 14' having a thickness corresponding to the track width; bonding layers for holding this metal magnetic film on either side; a gap material 21'; and an adhesion layer M' (consisting of resin or glass) for bonding the laminate-type magnetic head block 1' to the slider block 2'. Thus, the area of those material portions other than the slider material which are exposed on the ABS 4 is substantially reduced.
However, upon closer examination on this flying magnetic head, the present inventors -have found that the adhesion layer M', which bonds the laminate magnetic head block 1' to the slider block 2' and which consists of resin or glass, involves the generation of a deep recess during the machining of the ABS portion. Such a deep recess leads to a substantial deterioration in terms of CSS characteristic.